The present invention relates to a television camera apparatus of digital type provided with a camera head and a camera control unit independently, or more in particular to signal transmission between the camera head unit and the camera control unit of a digital television camera apparatus having the image processing function such as flesh tone contour processing, the highlight processing and the chroma key processing.
A high-quality television camera apparatus used for professional use in broadcast stations and the like is generally configured of a camera head unit (hereinafter referred to as the head unit) and a camera control unit (hereinafter referred to as the CCU) independent of each other and coupled to each other through a cable.
In this conventional television camera, the image information obtained by imaging an object is generally processed by an analog method. In recent years, however, a camera system of digital processing type has come to be widely used. In such a camera system, a television camera in which the transmission between the head unit and the CCU is digitally processed has begun to find applications.
A typical example of the image processing in such a television camera is what is called the flesh tone contour processing (hereinafter referred to as the FTC processing) in which the degree of contour emphasis of only a specific hue portion of the picture such as the flesh tone portion of the human being, for example, is controlled independently.
The FTC processing is the processing for controlling the degree of contour emphasis correction of the image portion of the human flesh color. Since an excessive degree of contour emphasis correction would highlight wrinkles, the process is executed normally for weakening the contour emphasis degree.
This FTC processing is disclosed, for example, in JP-A-7-143510, U.S. Pat. No. 4,506,293, etc. (prior art (1)).
It is desirable to display a processed image on a monitor screen or the like to check whether the FTC process designated by the operator is correctly performed as to the image portion intended by the operator, i.e., the hue portion intended by the operator. For this purpose, the video signal that has been subjected to the FTC processing is transmitted from the head unit to the CCU and displayed on a color monitor screen or the like. In this case, when the video signal subjected to the FTC processing is displayed as it is on the color monitor screen or the like, however, it is difficult to check which image portion has been subjected to the FTC processing. In view of this, the brightness of the image subjected to the FTC processing is replaced by a predetermined level of brightness to obtain a video signal indicating an image range subjected to the FTC processing. The FTC processed image portion of the original video signal is replaced by this video signal to obtain a video signal for checking the FTC processing range, that is, an FTC processing range check video signal. Alternatively, the image portion subjected to the FTC processing (FTC processed image portion) is superimposed by a signal representing a white or black frame which surrounds the image portion subjected to the FTC processing (i.e., the video signal indicating an image range subjected to the FTC processing) to obtain the FTC processing range check video signal. Such a FTC processing range check video signal is displayed on a screen in order to facilitate such a checking of an image portion subjected to the FTC processing. FIG. 1 shows an example of the FTC processing range check video signal displayed on a monitor screen 100 in which the portion of a human image 102 subjected to the FTC processing is surrounded by a black frame 104. In this case, the image portion of the black frame represents the image produced by the video signal indicating the FTC processed image range, while the entire image added with the black frame represents the image produced by the FTC processing range check video signal.
The prior art (1) described above discloses no method of transmitting the video signal for checking the FTC processing range (FTC processing range check video signal) to the CCU.
In the prior art, at the time of checking the FTC processing image, the video signal added with the video signal indicating the FTC processing range (i.e., the FTC processing range check video signal) is transmitted through a main video line from the head unit to the CCU, in which case the FTC processing range check video signal is transmitted in place of the normal video signal added with no indication signal.
FIG. 2 shows an example configuration of a conventional television camera apparatus using such a transmission method, which is realized by SK-2000 of Hitachi Denshi Ltd. (prior art (2)), for example.
Such an apparatus has a general configuration including a head unit 1, a transmission unit 2 and a CCU 3.
The head unit 1 includes a head processing unit 4 with a TV camera and a pixel data replacing unit 11. The whole head unit is held by a pedestal or a dolly not shown through a table and constitutes a body of the TV camera.
The transmission unit 2, on the other hand, includes two parts coupled through a transmission cable having a main video line 2x and data lines 2a, 2b. One of the parts is included in the head unit 1 and the other part included in the CCU 3, both of which are responsible for data transmission between the head unit 1 and the CCU 3.
Further, the CCU 3 is configured of a CCU processing unit 7, a controller 10 and the other part of the transmission unit 2.
The controller 10 outputs a processing variable control signal A and a processing range indication control signal B making up a video processing control signal. These signals are transmitted to the head unit 1 through the transmission unit 2.
The processing variable control signal A is formed by two kinds of signals having variable values, that is, a signal A1 for setting the hue to be subjected to the FTC processing and a signal A2 indicating the degree of flesh tone contour correction (hereinafter referred to as the contour level), i.e. the degree of the FTC processing. The processing range indication control signal B is an on/off signal for controlling whether or not a video signal indicating the position and the range of the hue subjected to the FTC processing (FTC processing range) on the image is to be added to the original video signal.
The operation relating to the control signals for the FTC processing according to the above-mentioned prior art will be described below.
The controller 10 includes at least two volume knobs 10a1, 10a2 for generating a hue setting signal A.sub.1 and a contour level setting signal A.sub.2, respectively, making up the processing variable control signal A, and a range indication switch 10b for turning on/off the processing range indication control signal B.
These signals A, B are both generated by human operation, and therefore are signals substantially similar to a DC signal exhibiting a considerable temporal delay. The hue setting signal A.sub.1 and the contour level setting signal A.sub.2 are voltage signals continuously variable from 0 to 5 V, for example. The processing range indication control signal B, on the other hand, is a binary signal assuming values of a low level of 0 V and a high level of 5 V, for example. These control signals A, B are transmitted to the head unit 1 through the transmission unit 2. The processing variable control signal A is input to the head processing unit 4, and the range indication control signal B is input to the pixel data replacing unit 11.
First, the head processing unit 4 determines a hue to be subjected to the FTC processing in accordance with the voltage value of the hue setting signal A.sub.1. Then, in accordance with the voltage value of the contour level setting signal A.sub.2, the contour level of the particular hue is determined. These signals are used to subject the video signal to a predetermined flesh tone contour processing, and to produce a video signal V.sub.0 as a FTC-processed video signal. The video signal V.sub.0 is a multi-bit line scan signal equivalent to the D-1 signal having a 10-bit parallel digital recording format, for example.
The video signal V.sub.0 output from the head processing unit 4 is transmitted through the pixel data replacing unit 11 and the main video line of the transmission unit 2 to the CCU 3 and is input to the CCU processing unit 7. This signal is output as the main video signal and the operator video signal. The operator video signal is displayed on the monitor.
The operation of the pixel data replacing unit 11 is controlled by the processing range indication control signal B. When the signal B is at a low level, for example, the replacing unit 11 operates in a manner that the video signal V.sub.0 from the head processing unit 4 is output as it is. When the range indication control signal B is at a high level, on the other hand, the replacing unit 11 operates in a manner that an indication signal C indicating the position and the range of the video signal V.sub.0 output from the head processing unit 4 associated with the hue to be subjected to the FTC processing is used as a switching signal (key signal) such that the video signal indicating the FTC processed image range is synthesized with the video signal V.sub.0 from the head processing unit 4 and output as the FTC processing range check video signal V.sub.s (see FIG. 12). In this case, the replacing unit 11 serves in a manner that the brightness level of each pixel of the video signal V.sub.0 associated with the high-level of the indication signal C is replaced with a predetermined fixed value, and the video signal thus partially replaced by the video signal indicating the FTC processed image range is output as a video signal Vs for checking the processing range (i.e., an FTC processing range check video signal).
This pixel data replacing unit 11 is easily configured by use of a plurality of known selector circuit ICs such as model 74LS157 in parallel.
Specifically, a change-over switch of multi-point double-contact type is formed by combining these ICs as shown in FIG. 3. One of the two inputs X and Y including a plurality of bits is selected according to the logical level of the control input S, and the input thus selected is output.
More specifically, in FIG. 3, the pixel data replacing unit 11 includes n selector circuit ICs 111 to 11n. Each selector circuit IC has an AND gate 131 to 13n and a change-over switch 121 to 12n. The number n of the selector circuit ICs is ten when the video signal V.sub.0 is composed of 10-bit parallel digital data. Each of the change-over switches 121 to 12n of the selector circuit ICs 111 to 11a includes a terminal X supplied with a corresponding bit of the video signal V.sub.0 (that is, the input terminals X of the change-over switches 121 to 12n are supplied with MSB (most significant bit) to LSB (least significant bit), respectively, of the video signal V.sub.0), a terminal Y supplied with a corresponding bit of a replacement data (that is, the input terminals Y of the change-over switches 121 to 12n are supplied with MSB to LSB, respectively, of the replacement data), a terminal Z for outputting a corresponding bit of the video signal V.sub.0 or the processing range check video signal signal V.sub.s (that is, the output terminals Z of the change-over switches 121 to 12n output MSB to LSB, respectively of the signal V.sub.0 or V.sub.s, as the case may be), and a control input terminal S. Each of the AND gates 131 to 13n of the selector circuit ICs 111 to 11n is supplied with the indication signal C and the processing range indication control signal B, and applies the output thereof to the terminal S of the corresponding one of the change-over switches 121 to 12n to thereby control the corresponding one of the change-over switches 121 to 12n.
The replacement data is a ten-bit digital data, for example, corresponding to the brightness level of 100% in the case of displaying the video signal indicating the FTC processed image range of the processing range check video signal V.sub.s with the maximum brightness. In the case where the replacement data is displayed in a black frame, in contrast, is a ten-bit digital data corresponding to the minimum brightness level. The description that follows concerns the case in which the former data is used as the replacement data.
In this configuration, assume that the indication signal C is at high level and that the range indication control signal B is at high level. Each of the AND gates 131 to 13n produces a high-level output, so that the output terminal Z of each of the change-over switches 121 to 12n is turned to the input terminal Y and the ten-bit replacement data is output as the video signal indicating the FTC processed image range of the processing range check video signal V.sub.s. In the case where at least one of the indication signal C and the range indication control signal B is at low level, on the other hand, each of the AND gates 131 to 13n outputs a low-level signal, so that the output terminal Z of each of the change-over switches 121 to 12n is turned to the input terminal X and the ten-bit video signal V.sub.0 is output as it is.
As long as the range indication switch 10b of the controller 10 remains off and the range indication control signal B is at low level, therefore, the video signal V.sub.0 output from the head processing unit 4 is transmitted as it is to the CCU 3 through the main video line 2x of the transmission unit 2, and output as a main video signal. At the same time, it is displayed on a monitor, thus setting up the system ready for on-air operation.
When the operator manipulates the knobs 10a1 and 10a2 of the controller 10 and makes such adjustments as setting the hue or the contour level, the voltage value of the processing variable control signal A (A1, A2) output from the controller 10 is changed.
The voltage value of the processing variable control signal A is sent to the head processing unit 4 through the transmission unit 2. The hue and the contour level are changed in accordance with the operation of the controller 10. As a result, the required FTC processing can be accomplished.
On the other hand, assume that the operator desirous of checking the range subjected to FTC processing and has turned on the range indication switch 10b of the controller 10. The range indication control signal B output from the controller 10 rises to high level. This signal is applied to the AND gates 131 to 13n of the pixel data replacing unit 11 of the head unit 1 through the transmission unit 2. Consequently, as long as the signal B is at high level, the pixel data replacing unit 11 replaces the video signal V.sub.0 with a signal of predetermined level having a brightness of 100% by pixel during the period when the indication signal C from the head processing unit 4 remains at high level (i.e., the signal portion associated with the hue to be processed), whereby the processing range check video signal V.sub.s is produced (see FIG. 12).
In the process, the voltage level of the indication signal C output from the head processing unit 4 is as follows, for example. Specifically, the indication signal C assumes a high level of, say, 5 V in the range of the hue subjected to the FTC processing, and assumes a low level of, say, 0 V out of the range subjected to the FTC processing. The indication signal C thus has a signal format of a binary line scan signal.
By way of reference, the hue can be determined from the ratio of the levels between the R, G and B signals.
Therefore, the head processing unit 4 delivers the indication signal C with a voltage of 5 V only when the levels of the R, G and B signals are in the desired ratio corresponding to the hue set by the signal A.
As a result, the video signal V.sub.S replaced with a signal having a maximum brightness level in the range subjected to the FTC processing is sent to the CCU 3 through the main video line 2x of the transmission unit 2 of the head unit 1, and output as a main video signal and a operator video signal. A portion of the picture having a uniform maximum brightness subjected to the FTC processing is displayed on the monitor, thereby facilitating the checking of the range to be processed.
With the above-mentioned configuration, the procedure for manipulating the knobs 10a1, 10a2 and the switch 10b of the controller 10 by the operator will be explained.
(1) The range indication switch 10b is turned on and the flesh tone portion of a human being which is the currently-set range subjected to the FTC processing is displayed on the monitor. Specifically, the interior of the frame 104' which is the currently-set range is displayed with maximum brightness as shown in FIG. 1.
(2) The hue setting knob 10a1 is manipulated to adjust the flesh tone which is a hue subjected to the FTC proessing. Thus, an image of the frame 104' changes to an image of a frame 104 which corresponds to the hue thus adjusted so that the interior of the frame 104 is displayed with maximum brightness.
(3) Once the image area in the frame 104, i.e., the range subjected to the FTC processing is checked, the switch 10b is turned off and the interior of the frame 104 is restored to the original brightness level.
(4) The knob 10a2 for setting the contour level is manipulated and the contour level is adjusted while watching the image within the range subjected to the FTC processing.
The FTC processing is accomplished in this way.
Now, explanation will be made about a prior art (3) in which a chroma key signal is transmitted from the head unit to the CCU.
In many cases, the various video signals in the television camera apparatus are normally processed by the head unit and the signals thus processed are transmitted to the CCU.
In the process, the schemes for transmitting signals between the camera head unit and the CCU include the RGB scheme for transmitting the video signal in the form of R (red), G (green) and B (blue) signals directly, the brightness/color difference scheme in which the video signal is transmitted by being converted into the luminance (Y) signal and the color difference signal, and the composite scheme for transmitting the luminance signal and the color signal by being converted into a composite color signal (composite signal).
In recent years, a television camera apparatus for transmitting the video signal in digital signal format has come to be used in order to suppress the deterioration of the signal-to-noise ratio (S/N) and the waveform characteristics in the transmission unit between the camera head unit and the CCU. In the process, the transmission rate (transmission speed) of the digital signal is preferably maintained as low as possible from the viewpoints of cost, power consumption and stability.
Among the various transmission schemes described above, the transmission rate is highest for the RGB scheme, followed by the brightness/color difference scheme in which the bandwidth of the color difference signal is reduced to about one half that of the luminance signal for a reduced transmission rate. The transmission rate can be reduced most in the composite scheme.
These broadcasting television camera apparatuses sometimes require a specification corresponding to the chroma key technique as a method of image processing. In such a case, a configuration is necessary in which a chroma key used for image synthesis by insertion from the CCU can be produced together with the video signal.
In the prior art (2) described above, one of the main video signal and the FTC processing range check video signal is alternatively transmitted to the CCU through the main video line. The checking of the FTC processing can not be performed, therefore, during the period when the television camera apparatus is operated in an on-air state and so the main video signal is transmitted through the main video line.
Specifically, in the case where the FTC processing range check video signal is output from the camera head unit to the CCU for checking the FTC processing during the on-air operation of the camera apparatus, the main video signal and the monitor video signal output from the CCU are both undesirably the FTC processing range check video signal. As a result the FTC processing range check video signal is output as the main video signal from the television camera apparatus. Thus, during the on-air operation, the FTC processing range check video signal cannot be transmitted from the head unit, and therefore the checking of the range subjected to the FTC processing can not be performed.
In the prior art (2), therefore, the processing range can be checked only at the time of set-up of the camera before the on-air operation.
In a method proposed to solve this problem, a dedicated cable or the like for transmitting only an indication signal from the head unit to the CCU may be laid separately so that the indication signal C is transmitted through this dedicated cable to the CCU to produce the FTC processing range check video signal in the CCU. In this method, however, the head unit and the CCU are sometimes installed several hundred meters apart from each other. The provision of such a dedicated cable, therefore, is not considered to have a practical value as it requires considerable labor and cost.
The readjustment of the FTC processing and the like is indispensable even during the on-air operation. In recording outdoor sports or other similar events, for example, the change in the imaging conditions due to the change in weather or with time is unavoidable. In such a case, the readjustment of the FTC processing and the like is a must even during the on-air operation in order to maintain the image quality.
In the prior art (3) described above, no consideration is given to the compatibility between a specification corresponding to the chroma key technique of the television camera apparatus and such factors as cost, power consumption and stability. The problem, therefore, is that employment of the RGB scheme not satisfactory in stability, power consumption or cost is unavoidable as a television camera apparatus requiring a high image quality for broadcasting.
Specifically, if a chroma key signal of high accuracy is to be produced, wide-band R, G, B signals are required as a video signal which must be transmitted from the head unit to the CCU. In the prior art (3), the high transmission rate of the video signal poses the problem of low stability, large power consumption and high cost on the one hand, and makes it unavoidable to employ the RGB scheme liable to be limited in the cable length on the other.
In an alternative method proposed, the chroma key signal is generated from the R, G, B signals at the head unit, and the R, G, B signals are converted into a composite signal, for example, with the resulting chroma key signal and the composite signal being transmitted to the CCU. In such a case, however, if the chroma key signal is to be transmitted to the CCU without suspending the on-air video signal (composite signal), a dedicated cable or the like separate from the main video line is required for transmitting the chroma key signal from the head unit to the CCU. Like the prior art (2), therefore, this technique is not considered to have any practical value due to its high cost.
As described above, in a conventional television camera apparatus comprising a camera head unit for generating a digital video signal, a transmission unit for transmitting the digital video signal from the camera head unit and a camera control unit (CCU) for processing the digital video signal transmitted from the camera head unit through the transmission unit, in order to transmit an image processing signal such as a video signal indicating the FTC processed image range or a chroma key signal to the CCU without suspending the on-air video signal, a cable dedicated to the image processing signal is required to be provided separate from the main video line, which has no practical value due to its high cost.